I will see if I can come up with some photographic evidence on the 2 piece. You are right about the full flight suits seeming more popular, and easier to find pictures of on Google, etc. The more I go back in my memory bank, I'm starting to think my comments above might be misleading. I feel like my comments made it seem like I had knowledge of theater wide popularity of the aviation uniforms, but in reality I can only speak to my experience.
The aviation uniform thing started in our Forward Support Company (FSC) with the commander requesting approval to the Battalion CSM to allow 92F (fuel dudes) to wear the aviation uniforms on deployment, and also requesting the Central Issue Facility (CIF) issue these uniforms to his guys. The justification was that these guys would be driving fuel trucks on convoy operations, and needed flame resistant uniforms in the name of safety. Word spread that these guys would look different from the rest of the formation, but not to mess with them by order of the CSM. This got the gears spinning in the other companies about using flame resistant uniforms on mounted patrols etc. but this was strictly an "outside the wire" uniform. I doremember the 92Fs having the 2 piece uniforms.
I've had conversations with other buddies who served in a variety of units about non standard things allowed on deployments "outside the wire" such as "relaxed grooming standards", civilian hiking boots, baseball caps, and flight suits.
This kind of stuff would never get back to the battalion chain of command, be captured in photographs (other than personal ones), and would certainly never be cleared by PAO to be released as an "official Army photograph".